tests of atlas strip detector modules: beam, source, g4 simulations

April 21, 2023 Pavel Řezníček, [email protected], IPNP Charles University, Prague 1

Tests of ATLAS strip detector modules:Tests of ATLAS strip detector modules:beam, source, G4 simulationsbeam, source, G4 simulations

Pavel Řezníček

Content:

• ATLAS SCT modules

• Analog x binary readout

• Source tests x beam tests

• Testbeam simulation

• Source tests simulation


ATLAS SCT @ LHCATLAS SCT @ LHC


ATLAS SCTATLAS SCT- one of 3 inner detector subsystems: Pixel, SCT, TRT- length 5.6 m, diameter 1.2 m- rapidity coverage: 2.5- placed in solenoidal magnetic field 2 T- optical readout- involved in 2nd level trigger – holds data in pipelines for 3 s- provides 4 precise point measurement (16 x 580 m)- 4 barrel layers (2112 modules) and 2 x 9 forward wheels (1976 modules)- radiation environment – tests of modules irradiated @ PS by 3·1014 p(24 GeV)/cm2

- SCT modules requirements: efficiency > 99%, noise occupancy < 10-5

- 2 x 768 strips, 6/12 cm long- strip pitch 80 m (barrel), 54 ÷ 95 m (forward)- 2/4 64mmx64mmx285m p-on-n detectors (barrel)- opposite planes stereo angle 40 mrad- AC coupled readout- 2 x 6 readout chips (128 channels)- ~ 20 ns shaping time- calibration circuit (mV fC)- data compression- binary readout


Analog readoutAnalog readout Binary readoutBinary readout(digitized amplitude)(digitized amplitude) (scanned threshold)(scanned threshold)

- monoenergetic signal (for example calibration pulse) + Gaussian noise (zero mean signal): threshold scan results in s-curve with ~ noise and threshold of 50% efficiency = monoenergetic signal

- particles passing through the detector: energy loss fluctuations + particle energy spectrum

sources of signal: calibration pulse, MIP, - , laserworking conditions: threshold ~ 1 fC

Landau distribution 90Sr (90Y) - spectrum Testbeam threshold scan - test threshold scan

Calibration process, noise measurement

(QA tests of all modules)

Test of few

modules only


- source tests Testbeam

- relativistic electrons (kinetic energy < 2.2 MeV) - MIP (180 GeV pions)

- simple construction - expensive- various geometrical settings - also possible + strong magnetic field (1.56 T)- repeated tests (before and after irradiation) - only few (up to ~ 15) modules can be tested- available at any time - available ~ 3x14 days a year- quick measurement and analysis - slower measurement, complicated analysis

(alignment)- no particle track measurement (except DUT) - analogue telescopes (microstrip detectors)- angular spread of particle tracks, multiple scattering - parallel tracks

energy loss (Geant4)


- efficiency (not reliable at low thresholds) - efficiency (reliable at all thresholds)- median (threshold of 50% efficiency) - median

- noise occupancy (reliable measurement - noise occupancy and efficiency withinfrom QA tests – ENC in advance) specifications (99% efficiency, 5·10-4 noise occupancy)

- average width of strips clusters ……charge sharing, - angular and magnetic field dependence at 1 fC-electrons, threshold for (un)irradiated modules

crosstalk


- multiple scattering => stronger charge sharing => different results on both detector planes


- bias voltage dependence of medians for (un)irradiated modules


- checking bonding - dead or noisy channels can be found - dead and noisy channels are found as well, wrongusing standard QA tests, laser tests can be used as well bonding by using residuals (alignment, telescopes)

- detectorbehaviorat its edges

- wrong bonding - large clusters needed (incidence angle) - interstrip position dependences


SimulationSimulation

- histogram: deposited energy spectrum of 180 GeV pions from Geant4 simulation

- solid curve: integral of the spectrum

- dashed curve: efficiency threshold scan – result of digitization under Athena

Geant4 simulation

- to explain differences between source and beam tests- to compare simulation to newer beam tests results (2001)

Geant4 simulation – energy loss @ track segments, -electrons, multiple scattering, …

Athena digitization – S. Gadomski, detectors and electronics response, magnetic field

Digitization


Beam tests simulation – angular and bias dependenceBeam tests simulation – angular and bias dependence- median underestimated (can be fixed) and average cluster size @ 1fC overestimated (?), trends of angular and bias dependencies match

- bias dependence – depleted region, diffusion, drift time

- angular and magnetic field (0T blue line, 1.56T red line) dependence – charge sharing, track length

simulation

measurementsimulation

measurement


Beam tests simulation – interstrip position dependenceBeam tests simulation – interstrip position dependence

16 degrees incidence angle

perpendicular incidence

- pure simulation

- simulation corrected to particle track determination uncertainities (multiple scattering, telescopes resolution) and averaging over 6 m wide interval as in testbeam analysis- beam tests

- -dependencies: detailed study of the detectors- can be measured using laser (in development)- efficiency and average cluster size analyzed- low statistics @ beam tests

simulation

simulation

measurement

measurement


simulation (efficiency, cluster sizes) beam tests (blue) and source test (red)

Beam and source tests simulationBeam and source tests simulation- ratio of medians from beam tests to the source tests: simulation: 1.12 ± 0.02

measured: 1.11 ± 0.07

- source tests sensitivity to geometrical settings – low on the detector plane nearer to the radioactive source (both simulation and measurements)

tests of atlas strip detector modules: beam, source, g4 simulations

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